I would like to know whether "$_SERVER['PHP_SELF'];" can be used more than one time in a script? This is because I have 2 forms in a script therefore I used "self reference" twice but it is not working.

The problem ist not $_SERVER['PHP_SELF'], the problem is your script. It is completely wrong program logic and cannot work that way:

You have an if-clause if (isset($_POST['submit'])) { and inside that if-clause you evaluate the same $_POST array for 'update' if (isset($_POST['update'])) { - this is definately a contradiction and never TRUE, as both refer to a submit button (you can only press once at a time).

It looks like you have a wrong idea about FORMS and HTTP Requests are working. I think you should go for some tutorials and/or a good documentian, how HTTP is working. I cannot give you an explanation here, because it's quite a lot of stuff and obviously you are struggling with the basic concepts of HTTP.

Again, my problem is everything works fine except that the information is not changed even after I have edited and clicked the "update" button.

Am I doing something terribly wrong again?I am searching for a lot of tutorial and book. I just wish to generate a simple edit profile page as my boss told me to do so even I am not working in a web hosting/software firm.